We're so close! If we add just one letter we'll get a phaser! While paser sounds cool, too, phaser is far cooler. Because, let's face it, the phaser is way nicer than the Star Wars blasters. You never saw a blaster actually incinerate anyone, did you? No. No you didn't.
Particle Acceleration by Stimulated Emission of Radiation -- PASER for Short (Via AIP.org)